A synthetic board has been used for a building material to be used for a deck, a terrace, a fence, a handrail or a post of a building, a bench, etc., a core of a lining of a door or a core of a panel put on the floor of a luggage room, which is an interior part of a vehicle, etc. Such a synthetic board is made of a synthetic material obtained by mixing small chips of e.g. wood and an adhesive, followed by thermal compression molding, and for example, a wooden synthetic board such as an oriented strand board (OSB), a particle board or a medium density fiberboard (MDF), a synthetic board obtained by molding foam scraps, ground rubber, paper, cloth, rice hull or the like, a board obtained by molding plant fibers, and a synthetic board obtained by molding an inorganic lightweight aggregate have been known.
Further, a ceiling material for an automobile obtained by laminating a foamed polyurethane sheet, a glass chopped strand mat and a surface skin and the like, followed by thermo compression bonding has been known.
Heretofore, as a general purpose adhesive used for production of such a synthetic board or ceiling material for an automobile, a urea resin, a urea melamine resin or a phenol resin has been mainly used, however, from a synthetic board or a ceiling material for an automobile using such a general purpose adhesive, formaldehyde which is one of substances causing sick building syndrome is diffused, such being problematic.
To take measures against such a problem, use of an adhesive composition containing an organic polyisocyanate compound and a tertiary amine compound as a catalyst for curing the organic polyisocyanate compound has been attempted. In a case where an organic polyisocyanate adhesive is used, in general, the pot life of a mixture of the adhesive composition and small pieces of e.g. wood is relatively short, and accordingly workability at the time of production of a synthetic board tends to deteriorate. Although it is possible to prolong the pot life by reducing the catalyst amount, such tends to lower physical properties of the resulting synthetic board or lower the productivity due to an increase of the thermal compression time. Further, also with respect to a ceiling material for an automobile, when a laminate is produced by thermo compression bonding, the workability is deteriorated by a short pot life, or the thermo compression bonding time is increased by a prolonged pot life, thus leading to a decrease of the productivity.
In order to solve such problems, use of a catalyst (temperature sensitive catalyst) which has low catalytic activity at room temperature and exhibits catalytic activity at a specific temperature depending upon the molding temperature as a catalyst to be used for an organic polyisocyanate adhesive has been proposed (for example, Patent Documents 1 and 2).
Patent Document 1 discloses as such a temperature sensitive catalyst an organic acid salt catalyst of a cyclic amine compound, however, the catalyst is inferior in the solubility in a polyisocyanate compound as compared with an amine compound and is hardly uniformly dispersed in the adhesive composition, whereby no uniform reactivity is obtained in some cases. Further, Patent Document 2 discloses a catalyst comprising a complex of formic acid (and as the case requires, a C2-20 aliphatic monocarboxylic acid) and an aliphatic tertiary amine, however, this catalyst has a problem of corrosion of an apparatus by formic acid, and its alternative has been desired.